Electrolytic method and apparatus for cleaning strip

June 5, 1951 e. e. vona0a 2,556,017

ELECTROLYTIC METHOD AND APPARATUS FOR CLEANING STRIPS

Filed Jan. 29, 1947 2 Sheets-Sheet 1

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June 5, 1951 E. E. VONADA 2,556,017

ELECTROLYTIC METHOD AND APPARATUS FOR CLEANING STRIPS

Filed Jan. 29, 1947

Sh«et6-Sheet 2

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Patented June 5, 1951

2,556,017

UNITED STATES PATENT OFFICE

2,556,017

ELECTROLYTIC METHOD AND APPARATUS FOR CLEANING STRIP

Edwin E. Vonada, Cleveland, Ohio

Application January 29,1947, Serial No. 725,056

Claims. (Cl. 204—141)

This invention relates to a method and apr paratus for cleaning strip and more particularly to cleaning strip in vertical passes. Most of the electrolytic cleaning of metals in strip form is done in horizontal passes which requires a great deal of floor space and an excessive clearance between the electrodes and strip. Vertical cleaning passes have been used to a slight extent, but those in use also have various disadvantages. For example, the electrical hook-up is such that the maximum cleaning action is not obtained at all times. In addition, it is difficult to vary the operation to suit variable conditions.

It is an object of my invention to provide an electrolytic tank and an electrical hook-up therefor which operates uniformly at a high efficiency.

Another object is to provide a novel method of cleaning strip uniformly and efficiently.

These and other objects will be more apparent after referring to the following specification and attached drawings, in which:

Figure 1 is a schematic longitudinal section through the electrolytic tank;

Figure 2 is a view taken on the line II—II of Figure 1; and

Figure 3 is an enlarged detail showing the insulated connection between the top of the passageway and the removable electrode.

.Referring more particularly to the drawings, the reference numeral 2 indicates a rubber lined electrolytic tank having a chamber 4 in the lower part thereof. The chamber 4 is separated from the top part of the tank by means of insulation S and division plates 8. A rubber covered sink roll iG is positioned in the chamber 4 which has an inlet 12 for the electrolyte. The electrolyte used may be any prior art cleaning electrolyte. An insulating barrier 44 extends from the center division plate 8 to a deflector plate (6 at the top of the tank and divides the top of the tank into two chambers 13 and 28 which are insulated from each other. A constricted passageway 22 in chamber 4 8 is insulated from the rest of the tank by means of insulation 24 at the bottom thereof. Fastened to the outside of passageway 22 and to the sides of tank 2 are deflector plates 28. Within the passageway 22 are removable electrode liners .28 which may be adjusted for movement toward.and away from each other in any suitable manner. Insulation 3Θ separates the liners 28 from the passageway 22. A retricted passageway 32 in chamber 20 is insulated from the rest of the tank by insulation 34. Deflector plates 36 are fastened to the outside of passageway 32 and to the sides of tank .2. Renewable electrode liners 3 8 are adjustably mounted within the passageway -32 and are separated therefrom by insulation 40. An entry conductor roll 42 is mounted above chamber IB and a delivery conductor roll 44 is mounted above the chamber 20. 5 A hood 46 surrounds the rolls 42 and 44 and the top of the tank 2 for collecting the fumes from the cleaning operation. A conduit 48 leads from the hood 46 to an exhaust fan, not shown. The negative terminal of a generator 50 is connected 10 to the .entry conductor roll 42 and its positive terminal is connected to the electrode liners 28. A two-pole double throw knife switch 51 is inserted in the output circuit of generator 50 for reversing the polarity of electrode liners 28. A 1 β second generator 52 has its positive terminal connected to the roll .$4 and its negative terminal connected to the .electrode liners 38. A two-,poie double knife switch 53, similar to switch 51, is inserted in the output circuit of generator 52 20 for reversing the polarity of electrode liners 38.

The strip S enters the tank 2 over the entry conductor roll 42 and passes downwardly between .the electrode liners 28 which are so arranged .that the clearance between the electrodes and 25 the strip will give the most effective cleaning.

The strip then passes under the sink roll ,10, then upwardly between the electrode liners 38 and oyer the exit roll 44. Hold down rolls 54 are provided at each conductor roll to insure 30 good contact between the rolls and the strip.

The hold down roll for the exit conductor roll also prevents electrolyte drag out.

As shown in Figure 2, .the shaft 56 of the sink roll 40 passes through shaft seals 58 at .each g₅ ..end .of the tank, the shaft seals being insulated frein the tank 2 by means of insulation 60. The shaft 5,6 is mounted for rotation in bearings 62.

The electrolyte is circulated by means of a pump $1 which delivers it from a reservoir 66 ₄Q to the chamber 4 through the opening 42. Insulation 63 is provided to prevent .grounds and current leakage from, the reservoir_;66. The electrolyte.passes upwardly through the passageways 122 and-32 and over the surface of the strip S at 45 high velocity. The electrolyte solution then flows over the top of the passageways and cascades downwardly over the plates 26 and 36 .which aid in releasing the entrained gases in the electrolyte. Deflector plates L6 confine the 50 electrolyte within the tank. The electrolyte leaves the tank through_: conduits 70 which lead to the reservoir .66. Means for cleaning and .conditioning the electrolyte are preferably located ill the reservoir 66.

With .the generators 5fl and 52 connected as shown there_;are three principal; electric .circuits.

One extends from the positive .terminal of the

2.556.017 generator 50 to the anodes 28, through the electrolyte solution to the strip S, then to the entry conductor roll 42 and back to the negative terminal of generator 50. The second circuit extends from the positive terminal of generator s 52 to the conductor roll 44, then to the strip S, through the electrolyte solution, then to cathodes 38 and back to the negative terminal of generator 52. A third circuit extends from the positive terminal of generator 50 to the anodes 28, 10 through the electrolyte solution to cathodes 38, and then to the negative terminal of generator 52. From here the circuit passes from the positive terminal of generator 52 to the conductor roll 44, through the strip S to the conductor 16 roll 42 and back to the negative terminal of generator 50, thus connecting the two generators in series. Since the electrical current follows the path of least resistance, which path is between the strip and the closely spaced electrodes, the 20 first two circuits carry substantially all of the current and produce the electrolytic cleaning action. The current carried by the third circuit is infinitesimal compared to that of the first two circuits and will not result in any marked 25 heating of the strip or the electrolyte. Considerable heat is developed in the strip and the electrolyte between the electrodes where the cleaning action is taking place, but this heat is rapidly dissipated by the forced circulation of the elec- 30 trolyte solution. Since the electrical losses are held to a minimum by the complete insulation of the tank and the electrodes and by providing an insulating barrier between the down and UP passes of the strip, the system is very effl- 35 cient. The rate of liberation of the negative charged oxygen ions is only one-half that of the positive charged hydrogen ions so that maximum cleaning is obtained by having maximum . hydrogen evolution. However, practical opera- 40 tion requires periodic reversal of electrode polarities in order to reduce the deposit of impurities on the cathode and rapid deterioration of the anode. If both the electrodes 28 and 38 were arranged for maximum hydrogen evolution, the 45 rate of cleaning would be cut substantially in half when the polarity is changed. By using two generators connected as shown, hydrogen ions will be liberated at the cathodes 38 and oxygen ions at the anodes 28. When it becomes 50 necessary to reverse the polarities of the conductor rolls and electrodes in order to remove impurities built up on the cathodes and prevent undue deterioration of the anodes, the anodes become the cathodes and the cathodes 38 65 become the anodes. Thus, one set of cathodes and one set of anodes are present in the tank at all times so that the rate of cleaning always remains substantially the same. Greater flexibility of operation is also obtained by this ar- 50 rangement. For example, it may be determined at some later stage of the processing that the hydrogen evolved has an injurious effect on the finished product. By simply changing the polarities of both conductor rolls the same rate of 55 cleaning takes place, but an oxygen atmosphere is provided at the delivery end of the tank. The generators 50 and 52 are excited in such a manner that an approximately constant line speed to cleaning current ratio is maintained. 70

While one embodiment of my invention has been shown and described, it will be apparent that other adaptations and modifications may be made without departing from the scope of the following claims. 75